Note 6 - Allowances for Loan and Lease Losses and Real Estate Losses (Details) - Allowance for Losses on Real Estate Owned (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Allowance for Losses on Real Estate Owned [Abstract]
Balance—beginning of year	$ 8,794	$ 14,877
Provisions for estimated losses	1,513	726
Losses charged off	(3,732)	(6,809)
Balance—end of year	$ 6,575	$ 8,794

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Namespace Prefix:	bsf_
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Balance Type:	na
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For each period for which an income statement is required, disclosure of the changes in the allowance, including balances at end of period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.10(4))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 10

-Subparagraph 4

-Article 9

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of the valuation allowance for real estate owned that was applied in the period against the carrying amount of real estate owned that was sold, written down or written off.

+ References

+ Details

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Balance Type:	debit
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- Definition

Amount of expense recognized in the income statement for a decrease in valuation of real estate owned (REO).

+ References

+ Details

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Period Type:	duration